Forage harvesters are machines which chop crop gathered from a field into small pieces to produce animal feed. In the case of crops such as grass or alfalfa, these will have been pre-cut and left to dry in the sun, so that the crop need only be gathered by the harvester. With other crops, such as maize, the forage harvester may also be required to cut the crop. Thus, the harvesters may be fitted with different headers to suit the crop being harvested.
The crop, whether cut maize or gathered grass, is fed into a rotating knife drum or cutter which comminutes the product. With grass crops, this alone is sufficient to produce the desired forage. However, when harvesting maize for silage purposes, the cutting alone does not suffice due to the presence of kernels in the crop. The kernels need to be cracked in order to release the nutrient, as uncracked kernels are hard for animals to digest. As cutting alone is insufficient to crack all the kernels, the crop is additionally passed through a crop processor which comprises two closely adjacent rollers, typically having serrated surfaces, which rotate such that there is slippage between the adjacent surfaces. The gap between the rollers is set to suit the size of grain passing through and the speed, rotational energy of the rollers, relative movement and serration of the surfaces together ensure cracking of any kernels that are still intact after chopping by the cutter.
The momentum of the maize from the crop processor or the grass from the cutter, as the case may be, carries the crop into a blower which then propels it up a tower to a discharge spout through which it is discharged into a wagon or a trailer drawn by a separate vehicle driven alongside the harvester.
When chopping kernel-free crops, such as grass or alfalfa, the crop processor is not required and leaving it in place in the crop flow path results in its rollers being unnecessarily subjected to wear.
To avoid such wear, it has previously been proposed to remove the crop processor from the vehicle, but the size and weight of the crop processor make this a difficult and cumbersome task.
Another solution, disclosed in GB 2 414 373, is to pivot the crop processor away from its operative position in the crop path but to leave it on the vehicle in an inoperative position. In GB 2 414 373, in order to avoid blockages, the blower and the crop processor are connected to a common pivot frame so that as the crop processor is withdrawn from the crop flow path, the blower moves downwards to take its place.
Because the drive pulley of the blower needs to move between two different positions, a tensioning roller is required for the belt which transmits drive to the blower from the engine and the present invention seeks to provide a suitable belt tensioning system that is simple to install and to set up correctly.